In recent years, developments in microelectro-mechanical system (MEMS) technology have spurred the development of novel systems to detect protein. According to a method, first, a sample solvent is introduced into a channel which is fabricated in a micro fluid chip. Next, protein that is contained in the sample solvent is fractionated by electrophoresis. The sample solvent is then dried in the channel, and a matrix for promoting ionization is added to the solvent. Subsequently, the protein fractionated in the channel is detected by means of a Matrix Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS).
According to Non-Patent Documents 1 to 3 and Patent Document 1, a sample that contains a matrix is fractionated using a groove-shaped channel formed in the chip having a non-sealed structure, i.e., a structure that is open at the top thereof. Then, the solvent in the channel is dried, and the fractionated sample is crystallized together with the matrix in the channel. Subsequently, the channel is scanned with a laser so that the fractionated sample is subjected to laser desorption and ionization, and is then subjected to mass spectrometry using the MALDI-MS.
In such an analyzing method, a sample is in a liquid state when protein is fractionated by electrophoresis and is in a dried state during the mass spectrometry. Therefore, a sample requires continuous treatment from a liquid state to a dried state in a single channel. According to Non-Patent Document 1, a solvent in a liquid sample is left as it is after electrophoresis in order to be dried. According to Non-Patent Document 2, a solvent in a liquid sample is dried by air blow supplied at a room temperature or dried in vacuum after fractionation of protein. According to Non-Patent Document 3, a solvent in a liquid sample is dried by heating a chip up to 60° C., or is dried in vacuum in a vacuum chamber. Patent Document 1 discloses an example in which a solvent in a liquid sample is transferred into a vacuum chamber so that it is freeze-dried.
[Non-Patent Document 1] Ken Tseng et al., “Fabrication and design of open microchannels for capillary electrophoresis separations and matrix-assisted laser/desorption mass spectrometry”, Part of the SPIE Conference on Micro- and Nanofabricated Structures and Devices for Biomedical Environmental Applications 2, SPIE Vol. 3606 (1999), pp. 137-148[Non-Patent Document 2] Jun Liu et al., “Electrophoresis separation in open microchannels. A method for coupling electrophoresis with MALDI-MS”, Analytical Chemistry, Vol. 73 (2001), pp. 2147-2151[Non-Patent Document 3] Michelle L. S. Mok et al., “Capillary isoelectric focusing in pseudo-closed channel coupled to matrix assisted laser desorption/ionization mass spectrometry for protein analysis”, Analyst, Vol. 129 (2004), pp. 109-111[Non-Patent Document 4] Yasuhiro Horiike et al., “Creation of Health Care Chip Aiming at Separation and Analysis of Trace Amount of Whole Blood”, Medical Electronics and Bio Medical Engineering, Vol. 39, Special Edition 2 (2001), pp. 2 & 3[Patent Document 1] WO03/071263[Patent Document 2] Japanese Patent Laid-Open Publication No. 2002-310858